Transmission interlock



May i3, i941. o. E. FISHBURN TRANSMISSION INTERLOCK Filed Jan. le, 194i 2 Smets-sheet 1 May i3, ISM. o. E. FISHBURN TRANSMISSION INTERLOCK Filed Jan. 18, 1940 2 Sheets-Sheet 2 v NVENTOR s2/'Jura BY mgm/fam;

A TTORNEY Patented May 13, 1941 UNITED STATES PATENT oFEicE 2,242,027 TRANSMISSION INTERLGCK Otto E. Fishburn, Det Chrysler Corporation, corporation of Delaware Application January 18, 1940,

2 Claims.

This invention relates to improvements in variable speed transmission mechanism.

More particularly, the invention pertains to improved means for locking the shiftable members of a variable speed transmission mechanism against involuntary movement.

The principal object of the invention is to provide, in a change speed transmission mechanism, a positive interlock for the shiftable members thereof which will prevent undesired movement of said members without interference with their shifting functions.

An additional object of the invention is to provide in such a mechanism an interlock which is automatically actuated to inoperative position with respect to one of the shiftable members whenever the transmission selector member is manipulated to select the said member preparatory to accomplishing a shift.

A further object is to provide a transmission interlock which shall be rapid in operation and positive in its action, yet simple in construction.

Additional objects of the invention will be apparent from the following description.

Reference is made to the accompanying drawings which illustrate two embodiments of my invention, and in which:

Fig. 1 is a partial sectional view of a change speed transmission mechanism embodying the invention.

Fig. 2 is a sectional Fig. l.

Fig. 3 is a partial top plan view of the apparatus of Figs. 1 and 2.

Fig. 4 is a view similar form of the invention.

Fig. 5 is a partial top plan view of the Fig. 4 apparatus showing the parts in neutral position.

Fig. 6 is a view 5 of the Fig. 4 apparatus with the parts in one of their shifted positions.

' In the drawings, like reference characters designate corresponding parts in the following description. In Fig. l, I0 designatesthe input shaftof the transmission mechanism and II the output shaft. The former is adapted for driving connection to a vehicle motor through the usual clutch, and the latter is adapted for driving connection to the vehicle drive wheels.

The shaft IIJ carries at its end a gear I2 and a clutch member I3. The gear I2 is in constant mesh with a gear I4 carried by the countershaft I5, and the clutch member I3 is adapted to be engaged by a mating clutch member I6 to establish direct drive setting of the transmission.

View along line 2-2 of to Fig. 1 of'a modied roit, Mich.,

Highland Park,

assignor to Mich., a

Serial No. 314,530

I6 is slidably splined on the the output or tail shaft II which, in accordance with the usual practice, is piloted at its extreme inner end in a hollow bearing-receiving portion of the shaft III.

The shaft II has a gear I8 journalled thereon, a set of clutch teeth I1 being formed integrally with said gear. The teeth I1 are adapted for engagement by the slidable clutch member I6 and the gear I8 is constantly meshed with a countershaft gear Clutch member I6 is which rotatably receives the tines of a shift fork 2| carried by a shift rail 22, the latter being slidable in bosses 23 formed in the transmission casing.

It may thus be seen that the clutch member I6 may be shifted forwardly (or to the left of Fig. 1) to engage the teeth I3 whereupon the shaft III will drive the shaft II direct; the gear I8 rotating freely because of its journalled mounting on shaft II. By shifting the clutch member I6 to the rear into engagement with teeth I1, an intermediate speed setting of the transmission may be obtained, the drive passing from gear I2 to gear I4 thence to shaft Il through gears I9 and I8.

A low and reverse driving gear 24 is splined on shaft II by splines 25 and is slidable by a fork 26 which engages the groove 21. The gear 24 may be shifted forwardly into mesh with a countershaftvgear 28 to establish low speed setting of the transmission, or it may be shifted rearwardly into mesh with idler gear 29 to establish reverse setting, the idler gear being driven by a fourth countershaft gear 30.

The fork 26 is carried by a rail 3| which is slidable in the casing in a manner similar to rail 22. Suitable ball detents 32 are provided for engaging corresponding grooves 33 in the rails to releasably hold the shift rails in their various positions as is common in the art. An interlock pin 34 is adapted for alternate engagement with grooves 35 formed in each of the shift rails for locking one against movement When the other is shifted.

Shift forks 2I and 26 arexed against movement relative to rails 22 and 3| respectively by set screws 36 and each fork is provided with a notch, designated 3'1--38 respectively for receiving a shift element 39. The element 39 may be operated by any suitable mechanism that will impart to the element the necessary selection and shifting motions, it being understood that the element 39 is intended to be moved The clutch member inner end portion of transversely of the transmission casing for sev Vfor engagement with a notch 46 cut in lHi thereby stopping rail 3| lective engagement with either the rail 22 or the rail 3|, then axially to shift the selected rail.

wall 40 of the casing, as shown in Fig. 2.

Normally the spring 43 urges thelatch 4| into the position shown in the drawings with the ringer 45- engaged in the rail 3| and fork ment. When the shift element 39 is moved into to compress spring 43.

'Ihe aforesaid arrangement facilitates easy and ooth shifting of same time, the spring 43 will urge the nger 44 toward the notch 31 in fork 2|, thus transmitting a desirable feel back to the hand of the driver which informs hlm of the posltion of the parts.

the rail 22 against the interlock pin 34 and the shift element 39 will against movement.

Vcross over and pick nger of latch 4| will snap into engagement With the notch 45 thereby locking the rail 3| The element 39 may then up the rail 22 for the shift into second or intermediate speed.

When the parts are in neutral, which is the position shown in Figs. 1 and 3, the shift element 39 is in partial engagement with both the notch 31 and the notch 3B and inasmuch as the rail neutral bythe latch 4|, the rail in Figs. l', 2 and 3 would involve only a duplica- In Figs. 4 to 6, inclusive, the transmission shift rails 22 and 3| are not slidable but are retained against axial movement by pins 50. The high and low speed shifter forks 2| and 26 respectively have enlarged portions designated 5| and adapted to receive the shift element 39.

Each of the fork portions is provided with a boss-like projection 532L which has a hollow bore in Which is disposedv iniuence of the spring 54.

The parts are designed in such manner that the pin 5S projects into the notch 53 Where it is adapted.' to be engaged by the shift element e9 upon movement of said element into said notch preparatory to shifting the member 5|. The rail 3| is provided which are adapted to be engaged by the ball when the member 5| is shifted to engage the gear 24 with either the low speed gear 28 or the reverse idler gear 23. As can be seen from Fig. 5, the ball 55 engages both the member 5| and the rail 5| when the parts are in neutral and prevents movement of the member 5| rela-v tive to the rail 3|. Upon movement of the shift element 39 into the notch 53 preparatory to shifting the member 5| along the rail 3|', the member 39 engages the protruding outer end of the pin 56 and moves the pin inwardly which in turn compresses the spring 54 and moves ball 55 out of engagement with rail 3|'. The member 5| is thereby unlocked and may be shifted longitudinally of the rail 3|', the ball 55 rolling along the rail until it reaches one or the other of the depressions 58 in which it is adapted to engage and function as a releasable detent.

Fig. 6 shows the positions of the various parts when the member 5| has been shifted to establish reverse setting of the transmission which involves meshing the gear 24 with the reverse idler gear 29'. The ball 55 has engaged the right hand depression 58 of rail 3| to thereby assist in maintaining the member 5I in reverse drive position. The pin 56 is retained in noninterferingposition relative to the member 5| and the rail 3| by engagement with the inner sliding surface of the member 5|.

Upon movement of the member 5I toward the left of Fig. 6 the ball 55 will engage the pin 56 when neutral position is reached to thereby lock the member 5| in neutral position unless shift element 39' is maintained in engagement with the notch 53 with sufficient pressure to overcome the pressure of the spring 54.

While it is usually necessary to provide the low-reverse shift fork or rail only with a lock means to prevent overtravel past neutral position, it is sometimes desirable to provide lock means for the second-high rail also and such is provided by the mechanism sho-wn in Figs. 4 to 6 inclusive. The member 52 is similar in construction to the member 5| and the lock means operates in an identical manner. When the parts are in neutral position as shown in Figs. 4 and 5, both of the pins 56 are urged to their limit of movement by the springs 54 and both of the balls 55 are in engagement with the relatively slidable members thereby locking both of the shift forks in neutral position. Either rail is unlocked as soon as the shift element 39' is moved into engagement with the corresponding notch preparatory to shifting thereof.

Although but two embodiments of my invention have been described, it is desired to point out that it is not my intention thereby to limit the invention in its broader aspects to the particular mechanism shown and described herein.

W'hat I claim is:

l. In a change speed transmission mechanism having a casing and |a rail fixed in said casing, a shift fork shftable along said rail and operable to establish different speed ratio drive-s; a shift finger adaptedI for movement into engagement with said fork for shifting the same along said rail; a spring urged detent ball carried by said fork; recesses in said rail for releasably receiving said ball thereby to yieldably lock said fork in ratio establishing positions; a recess in said rail for non-releasably receiving said ball thereby to positively lock said fork in neutral position; and means for forcing said ball out of said last mentioned recess upon movement of said finger into engagement with said fork whereby said fork is unlocked for shifting.

2. In a change speed transmission mechanism having a casing and a rail fixed in said casing, a shift fork shiftable along said rail and operable to establish different speed ratio drives; a shift finger adapted for movement into engagement with said fork for shifting the same along said rail; a spring urged detent ball carried by said forli; recesses in said rail for releasably receiving said ball thereby to yieldably lock said fork in ratio establishing positions; a recess in lsaid rail for non-releasably receiving said ball thereby to positively lock said fork in neutral position; a plunger carried by said rail having a head disposed in said last mentioned recess; said plunger being engageable by said shift finger on the Vmovement thereof to engage said fork to thereby push said ball out of said recess.

OTTO E. FISHBURN. 

